docs: def create_unique_disk_operation_id(dd, offsets):
          # type: (blobxfer.models.download.Descriptor,
          #        blobxfer.models.download.Offsets) -> str
          """Create a unique disk operation id
          :param blobxfer.models.download.Descriptor dd: download descriptor
          :param blobxfer.models.download.Offsets offsets: download offsets
          :rtype: str
          :return: unique disk id
          """
          return ';'.join(
              (str(dd.final_path), dd.entity._client.primary_endpoint,
               dd.entity.path, str(offsets.range_start))
          )